@Transactional的正确打开方式

经常用到事务管理，可还是不小心会写错，导致事务没有生效，这里总结下。

正确的代码例子如下所示，框架是使用spring+mybatis的，有些配置的就不贴出来了。

TestController2:

package com.test.controller;

import com.alibaba.fastjson.JSON;
import com.cy.service.UserService;
import com.test.dto.Child;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class TestController2 {

    @Autowired
    private UserService userService;

    /**
     * 测试transcation
     */
    @RequestMapping("/testTranscation.do")
    public void testTranscation(){
        String username = "小王";
        String password = "123455";
        userService.callAddUserMethod(username, password);
    }
}

UserService接口：

package com.cy.service;

import com.cy.entity.User;

/**
 * 用户Service接口
 * @author Administrator
 *
 */
public interface UserService {

    User login(User user);

    void addUserMethod(User user);

    void callAddUserMethod(String username, String password);
}

View Code

UserServiceImpl:　　　　

package com.cy.service.impl;

import com.cy.dao.UserDao;
import com.cy.entity.User;
import com.cy.service.UserService;
import org.springframework.stereotype.Service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.transaction.annotation.Transactional;
import javax.annotation.Resource;

/**
 * 用户Service实现类
 * @author Administrator
 *
 */
@Service("userService")
public class UserServiceImpl implements UserService {

    @Resource(name = "userService")
    private UserService userService;

    @Autowired
    private UserDao userDao;

    @Override
    public User login(User user) {
        return userDao.login(user);
    }

    @Override
    public void callAddUserMethod(String username, String password){
        User user = new User();
        user.setUsername(username);
        user.setPassword(password);
        try{
            userService.addUserMethod(user);
        }catch (Exception e){
            System.err.println("addUserMethod异常:" + e.getMessage());
            e.printStackTrace();
        }
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void addUserMethod(User user){
        int a = userDao.addUser(user);
        badMethod();
    }

    private void badMethod(){
        int i = 1/0;
    }

}

UserDao接口：

package com.cy.dao;

import com.cy.entity.User;

public interface UserDao {

    //登录
    User login(User user);

    Integer addUser(User user);
}

View Code

UserMapper.xml(这里属于不重要的配置)

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.cy.dao.UserDao">

    <select id="login" parameterType="User" resultType="User">
        select * from t_user where username=#{username} and password=#{password}
    </select>

    <insert id="addUser" parameterType="User">
        INSERT INTO
            t_user(
                username,
                password
            )
        VALUES(
            #{username},
            #{password}
        )
    </insert>
</mapper>

View Code

applicationContext.xml(这里属于不重要的配置，但是事务管理的配置重要)

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:jee="http://www.springframework.org/schema/jee"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="
        http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee.xsd
        http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">

    <!-- 自动扫描 -->
    <context:component-scan base-package="com.cy.service,com.test.service" />

    <!-- 配置数据源 -->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/demodb"/>
        <property name="username" value="root"/>
        <property name="password" value="root"/>
    </bean>

    <!-- 配置mybatis的sqlSessionFactory -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource" />
        <!-- 自动扫描mappers.xml文件 -->
        <property name="mapperLocations" value="classpath:com/cy/mappers/*.xml"></property>
        <!-- mybatis配置文件 -->
        <property name="configLocation" value="classpath:mybatis-config.xml"></property>
    </bean>

    <!-- DAO接口所在包名，Spring会自动查找其下的类 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.cy.dao" />
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"></property>
    </bean>

    <!-- (事务管理)transaction manager, use JtaTransactionManager for global tx -->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
    </bean>
    <tx:annotation-driven transaction-manager="transactionManager" proxy-target-class="true"/>

</beans>

mybatis-config.xml:（这个是完全不重要的配置）

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 别名 -->
    <typeAliases>
        <package name="com.cy.entity"/>
    </typeAliases>

</configuration>

View Code

测试：

在浏览器中输入：http://localhost:8088/testTranscation.do，发现"小王"并没有被插入数据库，因为报异常回滚掉了。

console中可以看到事务的回滚rollback：

  2019-03-29 14:41:52,411 [http-nio-8088-exec-3] DEBUG [org.springframework.jdbc.datasource.DataSourceTransactionManager] - Acquired Connection [com.mysql.jdbc.JDBC4Connection@3f44f876] for JDBC transaction
  2019-03-29 14:41:52,435 [http-nio-8088-exec-3] DEBUG [org.springframework.jdbc.datasource.DataSourceTransactionManager] - Switching JDBC Connection [com.mysql.jdbc.JDBC4Connection@3f44f876] to manual commit
  14:41:53.328 [http-nio-8088-exec-3] DEBUG org.mybatis.spring.SqlSessionUtils - Creating a new SqlSession
14:41:53.353 [http-nio-8088-exec-3] DEBUG org.mybatis.spring.SqlSessionUtils - Registering transaction synchronization for SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5453248e]
14:41:53.384 [http-nio-8088-exec-3] DEBUG org.mybatis.spring.transaction.SpringManagedTransaction - JDBC Connection [com.mysql.jdbc.JDBC4Connection@3f44f876] will be managed by Spring
14:41:53.437 [http-nio-8088-exec-3] DEBUG com.cy.dao.UserDao.addUser - ==>  Preparing: INSERT INTO t_user( username, password ) VALUES( ?, ? ) 
14:41:53.668 [http-nio-8088-exec-3] DEBUG com.cy.dao.UserDao.addUser - ==> Parameters: 小王(String), 123455(String)
14:41:53.669 [http-nio-8088-exec-3] DEBUG com.cy.dao.UserDao.addUser - <==    Updates: 1
14:41:53.669 [http-nio-8088-exec-3] DEBUG org.mybatis.spring.SqlSessionUtils - Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5453248e]
14:41:59.161 [http-nio-8088-exec-3] DEBUG org.mybatis.spring.SqlSessionUtils - Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5453248e]
14:41:59.161 [http-nio-8088-exec-3] DEBUG org.mybatis.spring.SqlSessionUtils - Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@5453248e]
2019-03-29 14:41:59,161 [http-nio-8088-exec-3] DEBUG [org.springframework.jdbc.datasource.DataSourceTransactionManager] - Initiating transaction rollback
  2019-03-29 14:41:59,161 [http-nio-8088-exec-3] DEBUG [org.springframework.jdbc.datasource.DataSourceTransactionManager] - Rolling back JDBC transaction on Connection [com.mysql.jdbc.JDBC4Connection@3f44f876]
  2019-03-29 14:41:59,259 [http-nio-8088-exec-3] DEBUG [org.springframework.jdbc.datasource.DataSourceTransactionManager] - Releasing JDBC Connection [com.mysql.jdbc.JDBC4Connection@3f44f876] after transaction
  2019-03-29 14:41:59,259 [http-nio-8088-exec-3] DEBUG [org.springframework.jdbc.datasource.DataSourceUtils] - Returning JDBC Connection to DataSource
  addUserMethod异常:/ by zero
java.lang.ArithmeticException: / by zero
    at com.cy.service.impl.UserServiceImpl.badMethod(UserServiceImpl.java:51)
    at com.cy.service.impl.UserServiceImpl.addUserMethod(UserServiceImpl.java:47)

总结：　　　　　　　　

1.@Transactional方法为接口方法，有异常往外抛。（addUserMethod必须为接口方法）

2.@Transactional方法中可以有私有方法，有异常往外抛。(badMethod)

3.调用@Transactional的方法，可以对它try catch，且必须是接口.方法来调用。（callAddUserMethod中调用addUserMethod，必须是userService.addUserMethod，userServiceImpl把自己注进来）

4.配置文件中必须要有事务管理的配置，缺一不可：

<!-- (事务管理)transaction manager, use JtaTransactionManager for global tx -->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource" />
    </bean>
    <tx:annotation-driven transaction-manager="transactionManager" proxy-target-class="true"/>

5.@Transactional方法里面不要try catch异常，但是可以声明throws Exception；

@Transactional方法里面的方法也同样往外抛异常

UserService:

public interface UserService {

    User login(User user);

    void addUserMethod(User user) throws ArithmeticException;

    void callAddUserMethod(String username, String password);
}

View Code

UserServiceImpl:

package com.cy.service.impl;

import com.cy.dao.UserDao;
import com.cy.entity.User;
import com.cy.service.UserService;
import org.springframework.stereotype.Service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.transaction.annotation.Transactional;
import javax.annotation.Resource;

/**
 * 用户Service实现类
 * @author Administrator
 *
 */
@Service("userService")
public class UserServiceImpl implements UserService {

    @Resource(name = "userService")
    private UserService userService;

    @Autowired
    private UserDao userDao;

    @Override
    public User login(User user) {
        return userDao.login(user);
    }

    @Override
    public void callAddUserMethod(String username, String password){
        User user = new User();
        user.setUsername(username);
        user.setPassword(password);
        try{
            userService.addUserMethod(user);
        }catch (Exception e){
            System.err.println("addUserMethod异常:" + e.getMessage());
            e.printStackTrace();
        }
    }

    @Transactional(rollbackFor = Exception.class)
    @Override
    public void addUserMethod(User user) throws ArithmeticException{
        int a = userDao.addUser(user);
        badMethod();
    }

    private void badMethod() throws ArithmeticException{
        try{
            int i = 1/0;
        }catch (ArithmeticException e){
            throw e;
        }
    }

}

transcation事务也是生效的。

6.注意，对于truncate table语句，可能在事务管理中不会生效：

对于mysql，必须要5.7版本以上，MySQL InnoDB中TRUNCATE理论上可以回滚（5.7+版本）。低于5.7版本改成用delete from table_name代替，delete语句是100%可以回滚的。

7.自调用会导致事务失效的例子：

@Transactional self-invocation (in effect, a method within the target object calling another method of the target object) does not lead to an actual transaction at runtime

@Transactional 自调用会导致事务失效‌，因为 Spring 事务是通过代理机制实现的，同一个类内部方法直接调用时绕过了代理对象，事务拦截器无法生效。‌‌‌在Spring框架中，@Transactional 注解用于声明事务管理。当你在一个类的方法上使用 @Transactional注解时，Spring 会为这个方法创建一个事务代理。这意味着方法的调用实际上是通过代理对象来转发的，以便Spring可以管理事务。

然而，当一个 @Transactional 注解的方法在同一个类的内部调用另一个 @Transactional 注解的方法时，这种调用被称为“自调用”（self-invocation）。在这种情况下，Spring事务代理不会介入，因为代理对象没有被创建，或者调用没有通过代理对象转发。因此，内部调用的方法不会被视为在一个事务的上下文中执行，这可能导致预期之外的行为，特别是当涉及到事务的传播和回滚时。官方文档明确说明‌：Spring 官方文档指出，只有"external method calls coming in through the proxy"（通过代理进入的外部方法调用）才会被拦截，自调用不会在运行时产生实际事务。‌‌‌

参考博客：

https://www.cnblogs.com/doubleflower/p/14898980.html

https://blog.csdn.net/m0_57921272/article/details/149559318

如何解决呢？

采用自注入，在service中将自身注入，在方法调用前加上self.method():

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Lazy;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
@Slf4j
public class OrderServiceImpl implements OrderService {

	@Autowired
    @Lazy
    private OrderService OrderService;
	
	@Override
    public void saveOrder(OrderRequest request) {
		OrderEntity entity = OrderService.save(request);
		
		...
	}
	
	@Override
    @Transactional(rollbackFor = Exception.class)
    public OrderEntity save(OrderRequest request) {
        //新增订单表
        Date date = new Date();
        OrderEntity entity = new OrderEntity();
        BeanUtil.copyProperties(request, entity);
        entity.setCreateTime(date);
        orderMapper.insert(entity);
}

@Lazy可以解决循环依赖（Circular Dependency）
当 A 依赖 B，B 又依赖 A 时，Spring 默认会报错。如果在其中一个注入点（如构造器参数或 Setter 方法）加上 @Lazy，Spring 会先注入一个代理对象，等到真正使用时再获取完整的 Bean，从而打破循环。

posted on 2019-03-29 14:37 有点懒惰的大青年阅读(2751) 评论(0) 收藏举报